Yes you can have direct debit of a balance due on an amended return and yes you can enter the DD info into the system however TT doesn't make the payment. The payment info is sent to the IRS with the 1040X and they are the responsible party to complete the debit as requested. If the amended return has been accepted for processing it could take a while for the debit to happen as they are woefully behind again this year.
If you save a PDF with all the worksheets you should see the debit request in the filing instructions. And ignore the 1040-V as it is not used with the 1040X.
